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Trane RTAA 215// circuit a,b intermittent low oil flow codes 199

I have read and lurked here for a while before posting for help. Background on the unit is 220 ton chiller system 1998 vintage with dual screws. The unit is intermittently shutting down either circuit A or B from time to time with no rhyme or reason and it never acts up while I'm onsite to catch it. Right now it's 83 degrees here and dropping to 60 or so at night. Sometimes it will go for days perfectly without a problem.

All condenser fans are running correctly operation verified
25lb of pressure drop across both circuit oil filters
UCM has updated program and OAT sensor installed
Oil level is spot on in both oil coolers
All electrical connections on oil DP switch have been verified
Compressors are starting at 40% load and then modulating up to around 70%

Condenser is visibly clean but I'm going to wash it out tomorrow to get a baseline on it.

I have not physically tested the oil pressure DP switch's yet.

But when it was 112-114 degrees this summer it ran like a top without a problem it's only once the weather cooled off in the last month these stinkin little gremlins are showing up. thanks for the help and any ideas are appreciated.

Condenser is visibly clean but I'm going to wash it out tomorrow to get a baseline on it.

I have not physically tested the oil pressure DP switch's yet.

If you had gone ahead and done these two things, it probably wouldn't have PO'ed graham for you to start this thread. As it is, he's probably choking on his beer right now and trembling too hard to type in his response.

I'd get these two items out of the way before doing anything else. Post your actual numbers on everything if you have to call back........

You can also find endless hours of reading on this subject and all of it's nuances simply by doing a site search on it.

How does the UCM logic work regarding this safety. While running it is looking for a minimum 50 lb differential and the contacts are closed. Does it test the integrity of the circuit in any other manner during operation and or shutdown process.

I don't have a clue what conditions are present when the failure is actually happening to determine if it is during system run or start up or some combination between.

Sure would be nice if it had freeze frame diagnostics like car control systems do.

How does the UCM logic work regarding this safety. While running it is looking for a minimum 50 lb differential and the contacts are closed. Does it test the integrity of the circuit in any other manner during operation and or shutdown process.

I don't have a clue what conditions are present when the failure is actually happening to determine if it is during system run or start up or some combination between.

Sure would be nice if it had freeze frame diagnostics like car control systems do.

All the UCM is doing, regarding this fault, is look at the DP switch contacts. If it opens, it calles out the fault. The DP switch should be set at 50 PSID + or - 5 (i set it at 55). Upon shutdown, the UCM closes the master oil solenoid valve and looks for the DP switch to open to test the integrity of the switch.

How does the UCM logic work regarding this safety. While running it is looking for a minimum 50 lb differential and the contacts are closed. Does it test the integrity of the circuit in any other manner during operation and or shutdown process.

I don't have a clue what conditions are present when the failure is actually happening to determine if it is during system run or start up or some combination between.

Sure would be nice if it had freeze frame diagnostics like car control systems do.

You might want to use the search feature there are several threads already covering the subject of oil pressure alarms. Maybe Jayguy will show up and see your thread, he doesn`t go postal all the time like Graham he was the nicer Trane guy.

All the UCM is doing, regarding this fault, is look at the DP switch contacts. If it opens, it calles out the fault. The DP switch should be set at 50 PSID + or - 5 (i set it at 55). Upon shutdown, the UCM closes the master oil solenoid valve and looks for the DP switch to open to test the integrity of the switch.

I`m wanting to say I heard that there was a bad batch of switches out there. Not sure how old this machine is or if it has ever had the problem addressed.

Everything about it looks stone stock. We'll give it a good bath and scrub behind the ears double check the pressure switch's and see what happens. I had a hunch I just wanted to hear someone else's opinions to back up my hunch. Thanks again.

...Maybe Jayguy will show up and see your thread, he doesn`t go postal all the time like Graham he was the nicer Trane guy.

'WAS' is right! now Graham is the nicest Trane guy!

check your oil pressure switch 'X' number...if it ends in '03' or '-03'...change it out as they tended to drift over time.

perform a very thorough checkout of the oil solenoid coil. if it is overheating or occasionally dropping out (bad wire nuts?) then this will cause the pressure switch to trip and of course, check out the pressure switch.

the foaming around Grahams mouth isn't from the beer!

Don't step on my favorite part of the Constitution just to point out your favorite part.

Political Correctness is forced on you because you have forgotten decency.